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README for Linux device driver for the IBM "C-It" USB video camera

INTRODUCTION:

This driver does not use all features known to exist in

the IBM camera. However most of needed features work well.

This driver was developed using logs of observed USB traffic

which was produced by standard Windows driver (c-it98.sys).

I did not have data sheets from Xirlink.

Video formats:

      128x96  [model 1]

      176x144

      320x240 [model 2]

      352x240 [model 2]

      352x288

Frame rate: 3 - 30 frames per second (FPS)

External interface: USB

Internal interface: Video For Linux (V4L)

Supported controls:

- by V4L: Contrast,  Brightness, Color, Hue

- by driver options: frame rate, lighting conditions, video format,

                     default picture settings, sharpness.

SUPPORTED CAMERAS:

Xirlink "C-It" camera, also known as "IBM PC Camera".

The device uses proprietary ASIC (and compression method);

it is manufactured by Xirlink. See http://www.xirlink.com/

http://www.ibmpccamera.com or http://www.c-itnow.com/ for

details and pictures.

This very chipset ("X Chip", as marked at the factory)

is used in several other cameras, and they are supported

as well:

- IBM NetCamera

- Veo Stingray

The Linux driver was developed with camera with following

model number (or FCC ID): KSX-XVP510. This camera has three

interfaces, each with one endpoint (control, iso, iso). This

type of cameras is referred to as "model 1". These cameras are

no longer manufactured.

Xirlink now manufactures new cameras which are somewhat different.

In particular, following models [FCC ID] belong to that category:

XVP300 [KSX-X9903]

XVP600 [KSX-X9902]

XVP610 [KSX-X9902]

(see http://www.xirlink.com/ibmpccamera/ for updates, they refer

to these new cameras by Windows driver dated 12-27-99, v3005 BETA)

These cameras have two interfaces, one endpoint in each (iso, bulk).

Such type of cameras is referred to as "model 2". They are supported

(with exception of 352x288 native mode).

Some IBM NetCameras (Model 4) are made to generate only compressed

video streams. This is great for performance, but unfortunately

nobody knows how to decompress the stream :-( Therefore, these

cameras are *unsupported* and if you try to use one of those, all

you get is random colored horizontal streaks, not the image!

If you have one of those cameras, you probably should return it

to the store and get something that is supported.

Tell me more about all that "model" business

--------------------------------------------

I just invented model numbers to uniquely identify flavors of the

hardware/firmware that were sold. It was very confusing to use

brand names or some other internal numbering schemes. So I found

by experimentation that all Xirlink chipsets fall into four big

classes, and I called them "models". Each model is programmed in

its own way, and each model sends back the video in its own way.

Quirks of Model 2 cameras:

-------------------------

Model 2 does not have hardware contrast control. Corresponding V4L

control is implemented in software, which is not very nice to your

CPU, but at least it works.

This driver provides 352x288 mode by switching the camera into

quasi-352x288 RGB mode (800 Kbits per frame) essentially limiting

this mode to 10 frames per second or less, in ideal conditions on

the bus (USB is shared, after all). The frame rate

has to be programmed very conservatively. Additional concern is that

frame rate depends on brightness setting; therefore the picture can

be good at one brightness and broken at another! I did not want to fix

the frame rate at slowest setting, but I had to move it pretty much down

the scale (so that framerate option barely matters). I also noticed that

camera after first powering up produces frames slightly faster than during

consecutive uses. All this means that if you use 352x288 (which is

default), be warned - you may encounter broken picture on first connect;

try to adjust brightness - brighter image is slower, so USB will be able

to send all data. However if you regularly use Model 2 cameras you may

prefer 176x144 which makes perfectly good I420, with no scaling and

lesser demands on USB (300 Kbits per second, or 26 frames per second).

Another strange effect of 352x288 mode is the fine vertical grid visible

on some colored surfaces. I am sure it is caused by me not understanding

what the camera is trying to say. Blame trade secrets for that.

The camera that I had also has a hardware quirk: if disconnected,

it needs few minutes to "relax" before it can be plugged in again

(poorly designed USB processor reset circuit?)

[Veo Stingray with Product ID 0x800C is also Model 2, but I haven't

observed this particular flaw in it.]

Model 2 camera can be programmed for very high sensitivity (even starlight

may be enough), this makes it convenient for tinkering with. The driver

code has enough comments to help a programmer to tweak the camera

as s/he feels necessary.

WHAT YOU NEED:

- A supported IBM PC (C-it) camera (model 1 or 2)

- A Linux box with USB support (2.3/2.4; 2.2 w/backport may work)

- A Video4Linux compatible frame grabber program such as xawtv.

HOW TO COMPILE THE DRIVER:

You need to compile the driver only if you are a developer

or if you want to make changes to the code. Most distributions

precompile all modules, so you can go directly to the next

section "HOW TO USE THE DRIVER".

The ibmcam driver uses usbvideo helper library (module),

so if you are studying the ibmcam code you will be led there.

The driver itself consists of only one file in usb/ directory:

ibmcam.c. This file is included into the Linux kernel build

process if you configure the kernel for CONFIG_USB_IBMCAM.

Run "make xconfig" and in USB section you will find the IBM

camera driver. Select it, save the configuration and recompile.

HOW TO USE THE DRIVER:

I recommend to compile driver as a module. This gives you an

easier access to its configuration. The camera has many more

settings than V4L can operate, so some settings are done using

module options.

To begin with, on most modern Linux distributions the driver

will be automatically loaded whenever you plug the supported

camera in. Therefore, you don't need to do anything. However

if you want to experiment with some module parameters then

you can load and unload the driver manually, with camera

plugged in or unplugged.

Typically module is installed with command 'modprobe', like this:

# modprobe ibmcam framerate=1

Alternatively you can use 'insmod' in similar fashion:

# insmod /lib/modules/2.x.y/usb/ibmcam.o framerate=1

Module can be inserted with camera connected or disconnected.

The driver can have options, though some defaults are provided.

Driver options: (* indicates that option is model-dependent)

Name            Type            Range [default] Example

--------------  --------------  --------------  ------------------

debug           Integer         0-9 [0]         debug=1

flags           Integer         0-0xFF [0]      flags=0x0d

framerate       Integer         0-6 [2]         framerate=1

hue_correction  Integer         0-255 [128]     hue_correction=115

init_brightness Integer         0-255 [128]     init_brightness=100

init_contrast   Integer         0-255 [192]     init_contrast=200

init_color      Integer         0-255 [128]     init_color=130

init_hue        Integer         0-255 [128]     init_hue=115

lighting        Integer         0-2* [1]        lighting=2

sharpness       Integer         0-6* [4]        sharpness=3

size            Integer         0-2* [2]        size=1

Options for Model 2 only:

Name            Type            Range [default] Example

--------------  --------------  --------------  ------------------

init_model2_rg  Integer         0..255 [0x70]   init_model2_rg=128

init_model2_rg2 Integer         0..255 [0x2f]   init_model2_rg2=50

init_model2_sat Integer         0..255 [0x34]   init_model2_sat=65

init_model2_yb  Integer         0..255 [0xa0]   init_model2_yb=200

debug           You don't need this option unless you are a developer.

                If you are a developer then you will see in the code

                what values do what. 0=off.

flags           This is a bit mask, and you can combine any number of

                bits to produce what you want. Usually you don't want

                any of extra features this option provides:

                FLAGS_RETRY_VIDIOCSYNC  1  This bit allows to retry failed

                                           VIDIOCSYNC ioctls without failing.

                                           Will work with xawtv, will not

                                           with xrealproducer. Default is

                                           not set.

                FLAGS_MONOCHROME        2  Activates monochrome (b/w) mode.

                FLAGS_DISPLAY_HINTS     4  Shows colored pixels which have

                                           magic meaning to developers.

                FLAGS_OVERLAY_STATS     8  Shows tiny numbers on screen,

                                           useful only for debugging.

                FLAGS_FORCE_TESTPATTERN 16 Shows blue screen with numbers.

                FLAGS_SEPARATE_FRAMES   32 Shows each frame separately, as

                                           it was received from the camera.

                                           Default (not set) is to mix the

                                           preceding frame in to compensate

                                           for occasional loss of Isoc data

                                           on high frame rates.

                FLAGS_CLEAN_FRAMES      64 Forces "cleanup" of each frame

                                           prior to use; relevant only if

                                           FLAGS_SEPARATE_FRAMES is set.

                                           Default is not to clean frames,

                                           this is a little faster but may

                                           produce flicker if frame rate is

                                           too high and Isoc data gets lost.

                FLAGS_NO_DECODING      128 This flag turns the video stream

                                           decoder off, and dumps the raw

                                           Isoc data from the camera into

                                           the reading process. Useful to

                                           developers, but not to users.

framerate       This setting controls frame rate of the camera. This is

                an approximate setting (in terms of "worst" ... "best")

                because camera changes frame rate depending on amount

                of light available. Setting 0 is slowest, 6 is fastest.

                Beware - fast settings are very demanding and may not

                work well with all video sizes. Be conservative.

hue_correction  This highly optional setting allows to adjust the

                hue of the image in a way slightly different from

                what usual "hue" control does. Both controls affect

                YUV colorspace: regular "hue" control adjusts only

                U component, and this "hue_correction" option similarly

                adjusts only V component. However usually it is enough

                to tweak only U or V to compensate for colored light or

                color temperature; this option simply allows more

                complicated correction when and if it is necessary.

init_brightness These settings specify _initial_ values which will be

init_contrast   used to set up the camera. If your V4L application has

init_color      its own controls to adjust the picture then these

init_hue        controls will be used too. These options allow you to

                preconfigure the camera when it gets connected, before

                any V4L application connects to it. Good for webcams.

init_model2_rg  These initial settings alter color balance of the

init_model2_rg2 camera on hardware level. All four settings may be used

init_model2_sat to tune the camera to specific lighting conditions. These

init_model2_yb  settings only apply to Model 2 cameras.

lighting        This option selects one of three hardware-defined

                photosensitivity settings of the camera. 0=bright light,

                1=Medium (default), 2=Low light. This setting affects

                frame rate: the dimmer the lighting the lower the frame

                rate (because longer exposition time is needed). The

                Model 2 cameras allow values more than 2 for this option,

                thus enabling extremely high sensitivity at cost of frame

                rate, color saturation and imaging sensor noise.

sharpness       This option controls smoothing (noise reduction)

                made by camera. Setting 0 is most smooth, setting 6

                is most sharp. Be aware that CMOS sensor used in the

                camera is pretty noisy, so if you choose 6 you will

                be greeted with "snowy" image. Default is 4. Model 2

                cameras do not support this feature.

size            This setting chooses one of several image sizes that are

                supported by this driver. Cameras may support more, but

                it's difficult to reverse-engineer all formats.

                Following video sizes are supported:

                size=0     128x96  (Model 1 only)

                size=1     160x120

                size=2     176x144

                size=3     320x240 (Model 2 only)

                size=4     352x240 (Model 2 only)

                size=5     352x288

                size=6     640x480 (Model 3 only)

                The 352x288 is the native size of the Model 1 sensor

                array, so it's the best resolution the camera can

                yield. The best resolution of Model 2 is 176x144, and

                larger images are produced by stretching the bitmap.

                Model 3 has sensor with 640x480 grid, and it works too,

                but the frame rate will be exceptionally low (1-2 FPS);

                it may be still OK for some applications, like security.

                Choose the image size you need. The smaller image can

                support faster frame rate. Default is 352x288.

For more information and the Troubleshooting FAQ visit this URL:

                http://www.linux-usb.org/ibmcam/

WHAT NEEDS TO BE DONE:

- The button on the camera is not used. I don't know how to get to it.

  I know now how to read button on Model 2, but what to do with it?

- Camera reports its status back to the driver; however I don't know

  what returned data means. If camera fails at some initialization

  stage then something should be done, and I don't do that because

  I don't even know that some command failed. This is mostly Model 1

  concern because Model 2 uses different commands which do not return

  status (and seem to complete successfully every time).

- Some flavors of Model 4 NetCameras produce only compressed video

  streams, and I don't know how to decode them.

CREDITS:

The code is based in no small part on the CPiA driver by Johannes Erdfelt,

Randy Dunlap, and others. Big thanks to them for their pioneering work on that

and the USB stack.

I also thank John Lightsey for his donation of the Veo Stingray camera.